This invention relates generally to improved method and apparatus for investigating subsurface conditions within a borehole traversing earth formations, and more particularly to improved techniques for measuring shut-in conditions within a subsurface production tube string.
In the past, it has been difficult to determine the shut-in temperature, pressure, and other physical conditions inside a narrow subsurface production tube. The narrow confines and extreme environmental conditions of the tube made accurate readings difficult. An early solution to this problem was to place a recorder down the tube to a specified depth to record the desired physical conditions within the tube at that depth and then remove the recorder to analyze the acquired data. This solution was unsatisfactory for two reasons: First, the extreme environmental conditions caused excessive recorder failure and/or the receipt of inaccurate results. Second, this procedure was of limited value in that there was a time delay before the recorder could be removed and physical conditions determined. Thus, instantaneous physical conditions inside the tube were not available using this procedure.
One object of this invention is to enable a surface facility to be able to determine at shut in conditions physical conditions inside the tube instantaneously through the use of an instrumentation package being placed inside the tube at a specified depth to transmit data related to the physical conditions inside the tube to a surface facility.
Another object of this invention is to enable the surface recording of the physical conditions within the tube at an unlimited number of depth positions inside the tube through the use of an instrumentation package combined with a tubing packoff tube. When triggered off by an longitudinal force, the tube packoff tool locks into the desired position inside the tube and isolates the instrumentation package below to permit accurate readings of the shut-in physical conditions within the tube over a period of time in a shut in condition. The tubing packoff tool may later be unlocked from its position, moved to another location inside the tube where the determination of physical conditions is also desired, and then relocked to again isolate the instrumentation package for additional readings. This procedure may be repeated an unlimited number of times.